package com.github.HarryHook.coding2017.jvm.cmd;

import java.util.ArrayList;
import java.util.List;

import com.github.HarryHook.coding2017.jvm.clz.ClassFile;

public class CommandParser {

    public static ByteCodeCommand[] parse(ClassFile clzFile, String codes) {

	if ((codes == null) || (codes.length() == 0) || (codes.length() % 2) != 0) {
	    throw new RuntimeException("the orignal code is not correct");

	}

	codes = codes.toUpperCase();

	CommandIterator iter = new CommandIterator(codes);
	List<ByteCodeCommand> cmds = new ArrayList<ByteCodeCommand>();

	while (iter.hasNext()) {
	    String opCode = iter.next2CharAsString();

	    if (ByteCodeCommand.new_object.equals(opCode)) {
		NewObjectCmd cmd = new NewObjectCmd(clzFile, opCode);

		cmd.setOprand1(iter.next2CharAsInt());
		cmd.setOprand2(iter.next2CharAsInt());

		cmds.add(cmd);
	    } else if (ByteCodeCommand.invokespecial.equals(opCode)) {
		InvokeSpecialCmd cmd = new InvokeSpecialCmd(clzFile, opCode);
		cmd.setOprand1(iter.next2CharAsInt());
		cmd.setOprand2(iter.next2CharAsInt());
		// System.out.println( cmd.toString(clzFile.getConstPool()));
		cmds.add(cmd);
	    } else if (ByteCodeCommand.invokevirtual.equals(opCode)) {
		InvokeVirtualCmd cmd = new InvokeVirtualCmd(clzFile, opCode);
		cmd.setOprand1(iter.next2CharAsInt());
		cmd.setOprand2(iter.next2CharAsInt());

		cmds.add(cmd);
	    } else if (ByteCodeCommand.getfield.equals(opCode)) {
		GetFieldCmd cmd = new GetFieldCmd(clzFile, opCode);
		cmd.setOprand1(iter.next2CharAsInt());
		cmd.setOprand2(iter.next2CharAsInt());
		cmds.add(cmd);
	    } else if (ByteCodeCommand.getstatic.equals(opCode)) {
		GetStaticFieldCmd cmd = new GetStaticFieldCmd(clzFile, opCode);
		cmd.setOprand1(iter.next2CharAsInt());
		cmd.setOprand2(iter.next2CharAsInt());
		cmds.add(cmd);
	    } else if (ByteCodeCommand.putfield.equals(opCode)) {
		PutFieldCmd cmd = new PutFieldCmd(clzFile, opCode);
		cmd.setOprand1(iter.next2CharAsInt());
		cmd.setOprand2(iter.next2CharAsInt());
		cmds.add(cmd);
	    } else if (ByteCodeCommand.ldc.equals(opCode)) {
		LdcCmd cmd = new LdcCmd(clzFile, opCode);
		cmd.setOperand(iter.next2CharAsInt());
		cmds.add(cmd);
	    } else if (ByteCodeCommand.bipush.equals(opCode)) {
		BiPushCmd cmd = new BiPushCmd(clzFile, opCode);
		cmd.setOperand(iter.next2CharAsInt());
		cmds.add(cmd);
	    } else if (ByteCodeCommand.dup.equals(opCode) || ByteCodeCommand.aload_0.equals(opCode)
		    || ByteCodeCommand.aload_1.equals(opCode) || ByteCodeCommand.aload_2.equals(opCode)
		    || ByteCodeCommand.iload_1.equals(opCode) || ByteCodeCommand.iload_2.equals(opCode)
		    || ByteCodeCommand.iload_3.equals(opCode) || ByteCodeCommand.fload_3.equals(opCode)
		    || ByteCodeCommand.voidreturn.equals(opCode) || ByteCodeCommand.astore_1.equals(opCode)) {

		NoOperandCmd cmd = new NoOperandCmd(clzFile, opCode);
		cmds.add(cmd);
	    } else {
		throw new RuntimeException("Sorry, the java instruction " + opCode + " has not been implemented");
	    }

	}

	calcuateOffset(cmds);

	ByteCodeCommand[] result = new ByteCodeCommand[cmds.size()];
	cmds.toArray(result);
	return result;
    }

    private static void calcuateOffset(List<ByteCodeCommand> cmds) {

	int offset = 0;
	for (ByteCodeCommand cmd : cmds) {
	    cmd.setOffset(offset);
	    offset += cmd.getLength();
	}

    }

    private static class CommandIterator {
	String codes = null;
	int pos = 0;

	CommandIterator(String codes) {
	    this.codes = codes;
	}

	public boolean hasNext() {
	    return pos < this.codes.length();
	}

	public String next2CharAsString() {
	    String result = codes.substring(pos, pos + 2);
	    pos += 2;
	    return result;
	}

	public int next2CharAsInt() {
	    String s = this.next2CharAsString();
	    return Integer.valueOf(s, 16).intValue();
	}

    }
}